Plasticized organic solvent soluble cellulosic film



Patented Aug. 26, 1941 PLASTICIZED' ORGANIC SOLVENT SOLUBLE CELLULO SIGFILM William D. R. Straughn, Kenmore, N. Y., assignor V to E. I. du Pontde Nemours & Company, Wilmington, Del., a corporation of Delaware vNoDrawing. Application September 1, 1939,

Serial No. 293,053 I 1 Claim. (01. 1os 1s9)' This invention relates toplasticized sheet material and the like; especially to plasticizedorganic derivatives of cellulose eminently suited for the manufacture ofthinfilm such as sheet wrapping material. More particularly, itappertains to compositions of matter comprising essentially celluloseacetate plasticized with isobutylene glycol.

Organic derivatives of cellulose, such' as organic solvent solublecellulose acetate, are not compatible with many of the plasticizersheretofore known and used in nitrocellulose compositions. In fact, up tothe present time relatively few compounds have been found to have thedesired compatibility necessary to enable them to combine with thesecellulosic materials to produce strong and flexible film of the thinnessdesirable for a sheet wrapping material. Furthermore, many of thecompounds which do satisfactorily produce flexibility and toughnessadversely affect other properties of the film, such as transparency, andare, therefore, unsatisfactory. In addition, some of the compoundseifecting favorable characteristics in freshly prepared film have only atemporary effect, and as a result, the plasticized material uponstanding gradually loses its flexibility and becomes brittle.

This invention had for an object the production of new compositions ofmatter suitable for the manufacture of permanently transparent, strongand flexible sheets or films, and the sheet material produced therefrom.A further object was to dry cast acetone soluble cellulose acetate intothin, strong, flexible sheets capable of retaining their physical andchemical characteristics. A general advance in the art, and otherobjects which will appear hereinafter, are also contemplated.

In the following description, general and specific, are disclosedcertain embodiments of the invention and details of What is believed tobe the best mode for carrying out the invention.

It has now been found that cellulose acetate and like organicderivatives of cellulose, when combined with isobutylene glycol, havingthe formula:

r i HOCCOH to enable air bubbles to work out of the solution), in}accordance with dry castingpractice, it was dry cast upon a smoothnickel casting wheel'(any other suitable film-formingsurface maybeicemployed) to produce a film, in a manner 'well known tothose'skilled in the art. The film so produced was transparent, strongand flexible.

In a second example of the invention, a medium viscosity ethyl cellulose(48.0% ethoxyl content) was utilized. The proportions were:

- Parts Ethyl cellulose 17.0 Isobutylene glycol 3.5 Solvent(ethanol-toluene 55:45) 79.5

A thin tough, transparent film resulted.

This invention is applicable to all kinds of organic derivatives ofcellulose which are soluble in organic liquids (solvents), includingcellulose esters such as cellulose acetate, cellulose propionate,cellulose butyrate, and the like; mixed esters, such as celluloseaceto-propionate, cellulose aceto-butyrate and the like; celluloseethers, such as methyl cellulose, ethyl cellulose, benzyl cellulose andthe like; mixed ethers, such as ethyl-benzyl cellulose and the like; andmixed cellulose ether esters such as ethyl cellulose acetate, and thelike.

If desired, 2:3-butane-diol, a di-hydroxy compound isomeric withisobutylene glycol, may also be utilized for its plasticizing effect.

Any suitable solvent for the composition may Y Ethylenedichloride-methanol :10 Methylene dichloride-methanol 90:10 Methylenedichloride-ethanol 90:10 Methylene dichloride-isopropanol 90:10

Methyl acetate, and Ethyl formate In practice the isobutylene glycol isincorporated in the cellulose acetate and like material to the extent offrom about 10% to 40% (based on the weight of the solid product formed).Preferably the formed product contains about 10% to 25 of theplasticizer. Isobutylene glycol is especially useful for softeningand/or plasticizing acetone-soluble cellulose acetate suoh as thatcontaining from 51% to 56% (or more broadly 46% to 56%) combined aceticacid.

The isobutylene glycol may be used in the cellulose derivativecomposition alone or in combination with other known plasticizers, suchas, for example, ethylene glycol mono-methyl ether adipate, ethyleneglycol mono-methyl ether phthalate, ethylene glycol mono-ethyl etherphthalate, ethylene glycol mono-butyl' ether phthalate, triethyleneglycol, tetraethylene glycol,

Although this invention has been described primarily from the standpointof the manufacture of sheeting or film for use as sheet wrappingmaterial, these compositions may be used for the manufacture ofphotographic film, plastics, lacquers, artificial straw, fine filamentsand yarns thereof suitable for textile uses and other products.

As many apparently widely difierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to the specificembodiments thereof except as defined in the appended claim.

I claim:

A thin, transparent, flexible film comprising essentially celluloseacetate of about 56% combined acetic acid content and isobutylene glycolin the ratio 22.5:7.5 by weight.

WILLIAM D. R. STRAUGHN.

